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Maruan Sahyoun commented on PDFBOX-4188: ---------------------------------------- [~gary.potagal] I've taken a quick look at the patch and would like to discuss some topics - PDFMergerUtility was using {{MemoryUsageSetting getPartitionedCopy}} where now the setting is passed on for each PDDocument and is no longer partitioned. So although the value used for {{MemoryUsageSetting}} is much lower now isn't that at the end the same result? - I haven't understood the main benefit of the changes done to {{MemoryUsageSetting}} and {{ScratchFile}}. What is the reason for these? - I think the patch should be divided in two parts - the changes to {{MemoryUsageSetting}} / {{ScratchFile}} and the changes to PDFMerger with test cases to show the improvements for each. - Do you see a benefit in using {{MappedByteBuffer}} - the handling of openAction doesn't belong into this patch. It should be part of a new issue. - the code doesn't follow the coding conventions https://pdfbox.apache.org/codingconventions.html so there is some effort to bring it in line with these. (I think that this section might be difficult to find on our website - any suggestions to make it easier to find the information is highly appreciated) Many of the questions are because this part of PDFBox is something I rarely touch - so I hope you're a little patient with me. > "Maximum allowed scratch file memory exceeded." Exception when merging large > number of small PDFs > -------------------------------------------------------------------------------------------------- > > Key: PDFBOX-4188 > URL: https://issues.apache.org/jira/browse/PDFBOX-4188 > Project: PDFBox > Issue Type: Improvement > Affects Versions: 2.0.9, 3.0.0 PDFBox > Reporter: Gary Potagal > Priority: Major > Attachments: PDFBOX-4188-MemoryManagerPatch.zip, > PDFBOX-4188-breakingTest.zip, PDFMergerUtility.java-20180412.patch > > > > Am 06.04.2018 um 23:10 schrieb Gary Potagal: > > We wanted to address one more merge issue in > org.apache.pdfbox.multipdf.PDFMergerUtility#mergeDocuments(org.apache.pdfbox.io.MemoryUsageSetting). > We need to merge a large number of small files. We use mixed mode, memory > and disk for cache. Initially, we would often get "Maximum allowed scratch > file memory exceeded.", unless we turned off the check by passing "-1" to > org.apache.pdfbox.io.MemoryUsageSetting#MemoryUsageSetting. I believe, this > is what the users that opened PDFBOX-3721 where running into. > Our research indicates that the core issue with the memory model is that > instead of sharing a single cache, it breaks it up into equal sized fixed > partitions based on the number of input + output files being merged. This > means that each partition must be big enough to hold the final output file. > When 400 1-page files are merged, this creates 401 partitions, but each of > which needs to be big enough to hold the final 400 pages. Even worse, the > merge algorithm needs to keep all files open until the end. > Given this, near the end of the merge, we're actually caching 400 x 1-page > input files, and 1 x 400-page output file, or 801 pages. > However, with the partitioned cache, we need to declare room for 401 x > 400-pages, or 160,400 pages in total when specifying "maxStorageBytes". This > would be a very high number, usually in GIGs. > > Given the current limitation that we need to keep all the input files open > until the output file is written (HUGE), we came up with 2 options. (See > PDFBOX-4182) > > 1. Good: Split the cache in ½, give ½ to the output file, and segment the > other ½ across the input files. (Still keeping them open until then end). > 2. Better: Dynamically allocate in 16 page (64K) chunks from memory or disk > on demand, release cache as documents are closed after merge. This is our > current implementation till PDFBOX-3999, PDFBOX-4003 and PDFBOX-4004 are > addressed. > > We would like to submit our current implementation as a Patch to 2.0.10 and > 3.0.0, unless this is already addressed. > > Thank you -- This message was sent by Atlassian JIRA (v7.6.3#76005) --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@pdfbox.apache.org For additional commands, e-mail: dev-h...@pdfbox.apache.org